Plasma processing apparatus having an evacuating arrangement to evacuate gas from gas-introducing part of a process chamber

ABSTRACT

A plasma processing apparatus can apply a high-quality process to an object to be processed by removing impurities from a gas-introducing part of a process chamber. The gas-introducing part connected to the process chamber so as to introduce a reactant gas into the process chamber. A first vacuum pump is connected to the process chamber so as to evacuate gas from the process chamber so that the process chamber is maintained at a negative pressure. A gas-evacuating arrangement is connected to the gas-introducing part so as to exclusively evacuate the reactant gas from the gas-introducing part. The gas-evacuating arrangement includes a second vacuum pump directly connected to the gas introducing part or a bypass passage connecting the gas-introducing par to the first vacuum pump by bypassing the process chamber.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to plasma processing apparatuses and, moreparticularly, to a plasma processing apparatus having a gas-introducingpart, which introduces a reactant gas into a process chamber.

2. Description of the Related Art

In recent years, a plasma processing apparatus is used to perform a filmdeposition process, an etching process or an ashing process in amanufacturing process of semiconductor devices since the semiconductordevices have become more densified and a finer structure. For example,in a typical microwave plasma processing apparatus, a 2.45 GHz microwaveis introduced into a process chamber through a slot electrode. An objectto be processed such as a semiconductor wafer or an LCD substrate isplaced inside the process chamber, which is maintained under a negativepressure environment by a vacuum pump. Additionally, a reactant gas isalso introduced into the process chamber so that the process gas isconverted into plasma by the microwave. Thus, active radicals and ionsare generated, and the radicals and ions react with the object to beprocessed, which achieves a film deposition process or an etchingprocess.

The reactant gas is introduced into the process chamber through gassupply nozzles provided on a sidewall of the process chamber.Alternatively, the reactant gas is introduced into the process chamberthrough a dielectric plate provided under a slot electrode, which isprovided on a top of the process chamber. The gas supply arrangementincluding such a gas supply nozzle or a dielectric plate is subjected toan evacuating process by a vacuum pump, which is provided to evacuategas inside the process chamber.

However, there is a problem in the conventional plasma processingapparatus in that residual impurities such as a water component cannotbe completely removed from inside the process chamber. A water componentadhering on the inner wall of the process chamber is evaporated due to avacuum being formed in the process chamber, and the water vapor isreleased to the atmosphere inside the process chamber. The water vaporis exhausted out of the process chamber by a vacuum pump. However, sincethe gas-introducing part provided to the process chamber hasgas-introducing holes (nozzles) each having a very small diameter, aremoval speed of the water component remaining inside thegas-introducing part is low. Accordingly, some amount of water componenttends to remain inside the gas-introducing part of the process chamber.

The water component remaining inside the gas-introducing part may enterand close the gas-introducing holes, which interrupts the introductionof the reactant gas into the process chamber. Thus, a yield rate of theobject to be processed is deteriorated. Additionally, if some of thegas-introducing holes are closed, this may deteriorate a uniformdistribution of the reactant gas in the process chamber, which mayresult in an uneven degree of processing of the object to be processed.Further, if the water component in the gas-introducing holes is ejectedinto the process chamber, the water component acts as an impurity, whichdeteriorates a high-quality process to be applied to the object to beprocessed.

SUMMARY OF THE INVENTION

It is a general object of the present invention to provide an improvedand useful plasma processing apparatus in which the above-mentionedproblems are eliminated.

A more specific object of the present invention is to provide a plasmaprocessing apparatus which can apply a high-quality process to an objectto be processed by removing impurities from a gas-introducing part of aprocess chamber.

In order to achieve the above-mentioned objects, there is providedaccording to one aspect of the present invention a plasma processingapparatus for applying a plasma process to an object to be processed,the plasma processing apparatus comprising a process chamber in whichthe object to be processed is subjected to the plasma process; agas-introducing part connected to the process chamber so as to introducea reactant gas into the process chamber; a first vacuum pump connectedto the process chamber so as to evacuate gas from the process chamber sothat the process chamber is maintained at a negative pressure; and agas-evacuating arrangement connected to the gas-introducing part so asto evacuate the reactant gas from the gas-introducing part.

According to the above-mentioned invention, the gas-evacuatingarrangement is connected exclusively to the gas-introducing part so asto evacuate the reactant gas remaining in the gas-introducing part.Thus, impurities such as a water component existing in thegas-introducing part can be evacuated from the gas-introducing parttogether with the reactant gas being evacuated by the gas-evacuatingarrangement that is exclusively provided to the gas introducing part.

In one embodiment of the present invention, the gas-evacuatingarrangement may comprise a second vacuum pump connected to thegas-introducing part. That is, the second vacuum pump, which isdifferent from the first vacuum pump, exclusively evacuates the reactantgas remaining in the gas-introducing part, which results in a rapid andefficient evacuation of the reactant gas remaining in thegas-introducing part.

In another embodiment of the present invention, the gas-evacuatingarrangement may comprise a bypass passage, which connects thegas-introducing part to the first vacuum pump by bypassing the processchamber. Accordingly, the gas-introducing part can be directly connectedto the first vacuum pump by the bypass passage by bypassing the processchamber, which results in a rapid and efficient evacuation of thereactant gas remaining in the gas-introducing part.

The gas-introducing part may have an annular shape and may beincorporated into a sidewall of the process chamber, and thegas-introducing part may have a plurality of circumferentially arrangednozzles through which the reactant gas is introduced into the processchamber.

Additionally, the gas-introducing part may comprise: at least one inletport from which the reactant gas is supplied; an annular gas passageconnected to the inlet port so that the reactant gas supplied from theinlet port is supplied to the plurality of nozzles by flowing throughthe annular gas passage; and an outlet port provided to the annular gaspassage so that the gas-evacuating arrangement is connected thereto.

Alternatively, the gas-introducing part may comprise a dielectric plateand a shower plate provided on a top of the process chamber so as tointroduce the reactant gas from the top of the process chamber, a gaspassage being formed between the dielectric plate and the shower plateso that the reactant gas flows through the gas passage and is introducedinto the process chamber through the shower plate. The dielectric platemay have an inlet port connected to the gas passage so as to supply thereactant gas to the gas passage, and the gas passage may have an outletport to which the gas-evacuating arrangement is connected.

The plasma processing apparatus according to the present invention mayfurther comprise a slot antenna having a plurality of slits so as toguide a microwave having a predetermined frequency which is determinedby the plasma process to be applied to the object to be processed. Adensity of the slits may be substantially uniform in a radial directionof the slot antenna.

Additionally, there is provided according to another aspect of thepresent invention a gas supply ring adapted to introduce a reactant gasinto a process chamber of a processing apparatus, the gas supply ringcomprising: a plurality of circumferentially arranged nozzles throughwhich the reactant gas is introduced into the process chamber; at leastone inlet port from which the reactant gas is supplied; an annular gaspassage connected to the inlet port so that the reactant gas suppliedfrom the inlet port is supplied to the plurality of nozzles by flowingthrough the annular gas passage; and an outlet port provided to theannular gas passage so that the reactant gas is evacuated from the gassupply ring through the outlet port.

According to the above-mentioned invention, a gas-evacuating arrangementcan be connected to the outlet port of the gas supply ring so as toevacuate the reactant gas remaining in the gas-introducing part. Thus,impurities such as a water component existing in the gas supply ring canbe evacuated from the gas supply ring together with the reactant gasbeing evacuated by the gas-evacuating arrangement that is exclusivelyprovided to the gas supply ring.

Additionally, there is provided according to another aspect of thepresent invention a dielectric plate adapted to be attached to a processchamber of a plasma processing apparatus, the dielectric platecomprising: a plurality of nozzles through which a reactant gas isintroduced into the process chamber; at least one inlet port from whichthe reactant gas is supplied; a gas passage connected to the inlet portso that the reactant gas supplied from the inlet port is supplied to theplurality of nozzles by flowing through the gas passage; and an outletport provided to the gas passage so that the reactant gas is evacuatedfrom the gas passage through the outlet port.

According to the above-mentioned invention, a gas-evacuating arrangementcan be connected to the outlet port of the dielectric plate so as toevacuate the reactant gas remaining in the gas passage formed in thedielectric plate. Thus, impurities such as a water component existing inthe gas passage can be evacuated from the gas passage together with thereactant gas being evacuated by the gas-evacuating arrangement that isexclusively provided to the dielectric plate.

Additionally, there is provided according to another aspect of thepresent inventions a plasma processing method comprising the steps of:evacuating gas from a process chamber by a first vacuum pump connectedto the process chamber; introducing a reactant gas into the processchamber through a gas-introducing part; applying a plasma process to anobject placed in the process chamber by generating plasma from thereactant gas stopping the introduction of the reactant gas into theprocess chamber after ending the plasma process; and evacuating thereactant gas remaining in the gas-introducing part by a second vacuumpump connected to the gas-introducing part.

Accordingly, the reactant gas remaining in the gas-introducing part canbe rapidly and efficiently evacuated from the gas-introducing part bythe second vacuum pump exclusive provided to the gas-introducing part.

Additionally, there is provided according to another aspect of thepresent invention a plasma processing method comprising the steps of:evacuating gas from a process chamber by a vacuum pump connected to theprocess chamber; introducing a reactant gas into the process chamberthrough a gas-introducing part having a plurality of nozzles; applying aplasma process to an object placed in the process chamber by generatingplasma from the reactant gas; stopping the introduction of the reactantgas into the process chamber after ending the plasma process; andevacuating the reactant gas remaining in the gas-introducing part by thevacuum pump by connecting the gas-introducing part to the vacuum pump bybypassing the process chamber.

Accordingly, the reactant gas remaining in the gas-introducing part canbe rapidly and efficiently evacuated from the gas-introducing part bythe first vacuum pump by a bypass passage that bypasses the processchamber.

Other objects, features and advantages of the present invention willbecome more apparent from the following detailed description when readin conjunction of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a structure of a microwave plasmaprocessing apparatus according a first embodiment of the presentinvention;

FIG. 2 is a block diagram of a temperature-adjusting device shown inFIG. 1;

FIG. 3 is a graph showing a nitrogen distribution in a direction of adepth when a multi-layered structure is formed on an object to beprocessed at a high temperature;

FIG. 4 is a graph showing a nitrogen distribution in a direction of adepth when a multi-layered structure is formed on an object to beprocessed at an appropriate temperature;

FIG. 5 is a graph showing a relationship between a defect density and atemperature of a silicon nitride film;

FIG. 6A is a plan view of a gas supply ring shown in FIG. 1;. FIG. 6B isa cross-sectional view taken along a line VI-VI of FIG. 6A;

FIG. 7 is a plan view of an example of a slot antenna shown in FIG. 1;

FIG. 8 is a plan view of another example of the slot antenna shown inFIG. 1;

FIG. 9 is a plan view of a further example of the slot antenna shown inFIG. 1;

FIG. 10 is a plan view of another example of the slot antenna shown inFIG. 1;

FIG. 11 is a graph showing a relationship between a transmission powerof a microwave and a thickness of a dielectric plate;

FIG. 12 is a graph showing a relationship between the thickness of thedielectric plate and an amount of isolation (sputtering rate) of thedielectric plate;

FIG. 13 is a graph shown in FIG. 11 with indication of ranges of thethickness of the dielectric plate;

FIG. 14 is a cross-sectional view of a showerhead having a gas supplyarrangement;

FIG. 15 is an enlarged cross-sectional view of a part of a shower platewhich part includes one of nozzles provided to the shower plate;

FIG. 16 is an enlarged cross-sectional view of an eject member providedwith a nozzle passage having a single nozzle opening;

FIG. 17 is an enlarged cross-sectional view of an eject member providedwith a nozzle passage having two nozzle openings;

FIG. 18 is an enlarged cross-sectional view of an eject member providedwith a nozzle passage having three nozzle openings;

FIG. 19 is an illustrative plan view of a cluster tool, which isconnectable to the microwave plasma processing apparatus shown in FIG.1;

FIG. 20 is an illustration of a structure of a microwave plasmaprocessing apparatus according to a second embodiment of the presentinvention; and

FIG. 21 is an illustration of an evacuating arrangement shown in FIG.20.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description will now be given, with reference to FIG. 1, of a firstembodiment of the present invention. FIG. 1 is an illustration of astructure of a microwave plasma processing apparatus 100 according tothe first embodiment of the present invention. The first embodiment ofthe present invention is specifically related to an evacuatingarrangement to evacuate gas from a gas-introducing part provided in aprocess chamber of the microwave plasma processing apparatus 100.

The microwave plasma processing apparatus 100 shown in FIG. 1 comprises:a gate valve 101 connected to a cluster tool 300; a process chamber 102which can accommodate a susceptor 104 on which an object to be processedsuch as a semiconductor wafer or an LCD substrate; a high-vacuum pump106 connected to the process chamber; a microwave supply source 110; anantenna member 120; and gas supply systems 130 and 160. It should benoted that a control system of the plasma processing apparatus 100 isnot illustrated in FIG. 1 for the sake of simplification.

The process chamber 102 is made of a conductive material such as analuminum alloy. In the present embodiment, the process chamber 102 has agenerally cylindrical shape. However the shape of the process chamber102 is not limited to the cylindrical shape, and any shape can beadopted unless the process chamber 102 is deformed by a vacuum formed inthe process chamber 102. The susceptor 104 is provided in the processchamber 102 so as to support the object W to be processed. It should benoted that an electrostatic chuck or a clamping mechanism to fix theobject W on the susceptor 104 is not illustrated in FIG. 1 for the sakeof simplification.

The susceptor 104 controls a temperature of the object W to be processedin the process chamber 102. The temperature of the susceptor 104 isadjusted to a value within a predetermined temperature range by atemperature-adjusting device 190. FIG. 2 is a block diagram of thetemperature-adjusting device 190 shown in FIG. 1. Thetemperature-adjusting device 190 comprises, as shown in FIG. 2, acontrol unit 191, a cooling jacket 192, a sealing member 194, atemperature sensor 196 and a heater unit 198. Cooling water is suppliedto the temperature control device 190 from a water source 199 such as awater line. The control unit 191 controls the temperature of the objectW to fall within a predetermined temperature range. In order to achievean easy control, it is preferable that the temperature of the coolingwater supplied by the water source 199 is constant.

For example, in a case in which a silicon nitride film (Si₃N₄) is to beformed on a silicon substrate as the object W (single layer nitridefilm), the control unit 191 controls the heater unit 198 so that thetemperature of the silicon substrate falls within a range from about450° C. to about 500° C. If the silicon substrate is not maintained at atemperature above 450° C., a dangling bond may occur which is notpreferable since a threshold voltage may vary as described later.

A consideration will be given of a case in which a silicon nitride filmis formed on a silicon oxidation film (SiO₂) after the silicon oxidationfilm is formed on the silicon substrate. In this case, an upper portionof the silicon oxidation film is converted into the silicon nitride filmby a plasma process by introducing nitrogen into the silicon oxidationfilm. In such a process, the control unit 191 controls the heater unit198 so that the temperature of the silicon substrate falls within arange from about 250° C. to about 350° C.

The reason for setting the temperature of the silicon substrate belowabout 350° C. is explained below with reference to FIG. 3. FIG. 3 is agraph showing a nitrogen distribution in a direction of a depth when amulti-layered structure is formed on an object to be processed at a hightemperature (for example, about 500° C.). As shown in FIG. 3, when thetemperature of the silicon substrate is set to a value greater than 350°C. by controlling the heater 198, a large amount of nitrogen isintroduced into an inner portion of the silicon oxidation film as wellas a surface (an upper portion) of the silicon oxidation film. It can beappreciated from FIG. 3 that nitrogen reaches a position 20 Å distantfrom the surface of the silicon oxidation film.

In such a case, nitrogen reaches a boundary between the siliconsubstrate and the silicon oxidation film, and a compound of silicon,oxygen and nitrogen is formed. The formation of the compound is notpreferable since the compound may deteriorate a performance of asemiconductor element formed on the silicon substrate. A rate ofnitrogen reaching the boundary between the silicon oxidation film andthe silicon substrate depends on the size of the semiconductor element.If a gate length is in the range of 0.18 μm to 0.3 μm as in theconventional semiconductor element, an influence of the nitrogen may benegligible. However, recent semiconductor element is reduced in its sizeand thus the gate length is reduced to, for example, 0.13 μm or 0.10 μm.Thus, the influence of the nitrogen will not be negligible.

On the other hand, if the temperature of the silicon substratecontrolled by the heater unit 198 is set to below 350° C., the nitrogenis distributed to an inner portion of the silicon oxidation film as wellas the surface (an upper portion) of the silicon oxidation film. FIG. 4is a graph showing a nitrogen distribution in a direction of a depthwhen a multi-layered structure is formed on an object to be processed atan appropriate temperature (for example, about 350° C.). It can beappreciated from FIG. 4 that the depth of the nitrogen is within anallowable range (less than 10 Å), and, therefore, the above-mentionedproblem can be eliminated by setting the temperature of the siliconsubstrate below 350° C.

The reason for setting the temperature of the susceptor 104 greater thanabout 250° C. is explained below. A CV characteristic which indicates arelationship between a gate voltage V and a gate capacitance C is oftenused as an index representing an operational characteristic of theobject W to be processed (semiconductor element). The CV characteristichas a hysteresis at a time when the gate voltage V is applied andreleased. If the hysteresis width is large, threshold voltages (voltageat which a semiconductor element turns on and off) of the gate voltage Vis varied, which deteriorates reliability. Accordingly, the hysteresiswidth is preferably maintained within a predetermined voltage range suchas less than 0.02 V. This may be applied to a layered structure. Thehysteresis width becomes larger as the number of defects (dangling bond)of the silicon nitride film increases. FIG. 5 is a graph showing arelationship between defect density of the silicon nitride film and thetemperature of the susceptor 104. In FIG. 5, a dotted line indicates anallowable defect density. In order to maintain the hysteresis width, thedefect density of the silicon nitride film must be maintained asindicated by a dotted line in FIG. 5. The inventors found that theallowable defect density is about 250° C. as interpreted from FIG. 5.

The control unit 191 controls the temperature of the susceptor 104 to beabout 450° C. for a CVD process and about at least 80° C. for an etchingprocess. In any case, the object W to be processed is maintained at atemperature at which a water component does not adhere to the object W.

The cooling jacket 192 is provided for supplying a cooling water so asto cool the object W to be processed during a plasma process. Thecooling jacket 192 is made of a selected material such as a stainlesssteel which has high heat conductivity and an easy machinability to forma water passage 193. The water passage 193 extends in longitudinal andtransverse directions of the cooling jacket 192 having a square shape,and the sealing members 194 are screwed into openings of the waterpassage 193. However, the shape of the cooling jacket 192 is not limitedto the square shape, and the cooling jacket 192 and the water passagecan be formed with any shape. It should be noted that a coolant such asalcohol, gulden or fluorocarbon may be used instead of the coolingwater. The temperature sensor 196 can be a known sensor such as a PTCthermister an infrared sensor or a thermocouple. The temperature sensormay either be connected or not connected to the water passage 193.

The heater unit 198 is comprised of a heater wire wound on a water pipeconnected to the water passage of the cooling jacket 192. By controllingan electric current supplied to the heater wire, the temperature of thecooling water flowing through the water passage 193 of the coolingjacket 192 can be adjusted. Since the cooling jacket 192 has high heatconductivity, the temperature of the cooling jacket is substantiallyequal to the temperature of the cooling water flowing through the waterpassage 193.

The susceptor 104 is movable in a vertical direction inside the processchamber. A vertically moving system of the susceptor 104 comprises avertically moving member, a bellows and a vertically moving mechanism.The vertically moving system can be achieved by any known structure inthis art. The susceptor 104 is moved up and down between a home positionand a process position. When the plasma processing apparatus 100 is notin operation or awaiting state, the susceptor 104 is located at the homeposition. The object W to be processed is transferred to the susceptor104 at the home position from the cluster tool 300 via the gate valve101, and vice versa. A transfer position other than the home positionmay be defined so as to communicate with the gate valve 101. A verticaltravel of the susceptor 104 can be controlled by a controller of thevertically moving mechanism or a control unit of the plasma processingapparatus 100, and the susceptor can be observed through a view port(not shown in the figure) provided to the process chamber 102.

The susceptor 104 is connected to a lifter pin vertically moving system(not shown in the figure). The lifer pin vertically moving systemcomprises a vertically moving member, a bellows and a vertically movingdevice. The vertically moving system can be achieved by any knownstructure in this art. The vertically moving member is made of aluminum,for example, and is connected to three lifer pins, which verticallyextend from vertices of an equilateral triangle. The lifter pins arevertically movable by penetrating the susceptor 104 so as to verticallymove the object W to be processed placed on the susceptor 104. Theobject W is moved in the vertical direction at a time when the object Wis put into the process chamber 102 from the cluster tool 300, and at atime when the object W after processing is taken out of the processchamber 102 and transferred to the cluster tool 300. The verticallymoving mechanism may be arranged to allow the vertical movement of thelifter pins alone when the susceptor 104 is at a predetermined positionsuch as the home position. Additionally, a vertical travel of the lifterpins can be controlled by a controller of the vertically movingmechanism or a control unit of the plasma processing apparatus 100, andthe movement of the lifter pins can be observed through a view port (notshown in the figure) provided to the process chamber 102.

A baffle plate may be provided to the susceptor 104 if necessary. Thebaffle plate may be vertically moveable together with the susceptor 104,or may be brought in engagement with the susceptor 104 at the processposition. The baffle plate separates a process space in which the objectW to be processed is placed from an exhaust space underneath the processspace. The baffle plate mainly serves to maintain a potential of theprocess space (that is, maintain a microwave in the process space) andmaintain a predetermined degree of vacuum (for example, 50 mTorr). Thebaffle plate is formed of pure aluminum, and has a hollow disk-likeshape. The baffle plate has a thickness of 2 mm, and has many throughholes arranged at random. Each of the through holes has a diameter ofabout 2 mm so that an open area ratio of the baffle plate is more than50%. It should be noted that the baffle plate could have a meshedstructure. Additionally, the baffle plate may have a function to preventa reverse flow from the exhaust space to the process space or a functionto create a pressure difference between the process space and theexhaust space.

The susceptor 104 is connected to a bias radio frequency power supply282 and a matching box (matching circuit) 284, and constitutes anion-plating device together with an antenna member 120. The bias radiofrequency power source 282 applies a negative direct current bias (forexample, a 13.5 MHz radio frequency) to the object W to be processed.The matching box 284 is provided to eliminate influences of a straycapacitance and a stray inductance of an electrode in the processchamber 102. The matching box, for example, uses a variable condenserarranged parallel and serial to a load. As a result, ions areaccelerated by the bias voltage toward the object W to be processed,resulting in promotion of the process by ions. The energy of the ions isdetermined by the bias voltage, and the bias voltage can be controlledby the radio frequency power. The frequency of the radio frequencyapplied by the power source 283 is adjustable in response to slits 210of a slot electrode 200.

The inside of the process chamber 102 is maintained at a predeterminednegative pressure by a high-vacuum pump 106. The high-vacuum pump 106uniformly evacuate gas from the process chamber 102 so as to maintainthe plasma density uniform so that the plasma is prevented from beinglocally concentrated to prevent a local change in a depth of a processedportion of the object W. Although the high-vacuum pump 106 is providedat a corner of a bottom of the process chamber 102 in FIG. 1, aplurality of high-vacuum pumps may be provided to the process chamber102, and the position of the high-vacuum pump 106 is not limited to theposition indicated in FIG. 1. The high-vacuum pump 106 is constituted,for example, by a turbo-molecular pump (TMP), and is connected to theprocess chamber 102 via a pressure adjust valve (not shown in thefigure). The pressure adjust valve is a known valve such as a so-calledconductance valve, gate valve or high-vacuum valve. The pressure adjustvalve is closed when the apparatus 100 is not in operation, and is openin operation so as to maintain the process chamber 102 at apredetermined pressure (for example, 0.1 to 10 mtorr) created by thehigh-vacuum pump 106.

It should be noted that, in the present embodiment shown in FIG. 1, thehigh-vacuum pump 106 is directly connected to the process chamber. Theterm “directly connected” means that the high-vacuum pump is connectedto the process chamber without a connecting member between thehigh-vacuum pump 106 and the process chamber 102. However, a pressureadjust valve can be provided between the high-vacuum pump 106 and theprocess chamber 102.

Gas supply rings 140 and 170 made of quartz pipes are provided to asidewall of the process chamber 102. The gas supply ring 140 isconnected to a reactant gas supply system 130. The gas supply ring 170is connected to a discharge gas supply system 170. The gas supply system130 comprises a gas supply source 131, a valve 132, a mass flowcontroller 134 and a gas supply line 136 interconnecting theaforementioned parts. Similarly, the gas supply system 140 comprises agas supply source 161, a valve 162, a mass flow controller 164 and a gassupply line 166 interconnecting the aforementioned parts.

For example, in order to deposit a silicon nitride film, the gas supplysource 131 supplies a reactant gas (or material gas) such as NH₃ orSiH₄, and the gas supply source supplies a discharge gas such as amixture gas produced by adding N₂ and H₂ to at least one of neon, xenon,argon, helium, radon and krypton. However, the gas supplied to theprocess chamber 102 is not limited to the above-mentioned gasses, andCl₂, HCl, HF, BF₃, SiF₃, GeH₃, AsH₃, PH₃, C₂H₂, C₃H₈, SF₆, Cl₂, CCl₂F₂,CF₄, H₂S, CCl₄, BCl₃, PCl₃ or SiCl₄CO may be supplied.

The gas supply system 160 may be omitted by replacing the gas supplysource 131 with a gas supply source, which can supply a mixture gasessupplied by the gas supply sources 131 and 161. The valves 132 and 162are open during a plasma processing period of the object W to beprocessed, and is closed during a period other than the plasmaprocessing period.

Each of the mass flow controllers 134 and 164 comprises a bridgecircuit, an amplifying circuit, a comparator circuit and a flow controlvalve, and controls a gas flow. That is, each of the mass flowcontrollers. 134 and 164 controls the flow control valve based on ameasurement of flow by detecting a transfer of heat from upstream todownstream due to the gas flow. However, any known structure other thanthe above-mentioned structure may be used for the mass flow controllers134 and 164.

Each of the gas supply passages 136 and 166 is formed of a seamless pipeand a bite type coupling or a gasket coupling is used so that impuritiesare prevented from entering the system through the gas supply passages136 and 166. Additionally, in order to prevent generation of particlesdue to dirt or corrosion inside the pipes, the gas supply passages 136and 166 may be coated by an insulating material such as PTFE, PFA,polyimide or PBI. Additionally, an electropolishing may be applied to aninner surface of the pipes forming the gas supply lines 136 and 166.Further a dust particle trap filter may be provided to the gas supplylines 136 and 166.

FIG. 6A is a plan view of a gas supply ring 140, and FIG. 6B is across-sectional view taken along a line VI-VI of FIG. 6A. As shown inFIGS. 6A and 6B, the gas supply ring 140 comprises: a ring-like housingor main part 146 which is made of quartz and attached to the sidewall ofthe process chamber 102; an inlet port 141 connected to the gas supplypassage 136; an annular gas passage 142 connected to the inlet port 141;a plurality of gas supply nozzles 143 connected to the gas passage 142;an outlet port 144 connected to the gas passage 142 and a gas exhaustpassage 138; and a nozzle part 145 which is made of quartz and fixed tothe sidewall of the process chamber 102.

The gas supply nozzles 143 arranged at an equal interval in acircumferential direction contribute to form an even gas flow within theprocess chamber 102. The gas-introducing means is not limited the gassupply ring 140, and a radial flow type or a showerhead type may beapplied as described later.

Gas inside the gas supply ring 140 can be evacuated trough the outletport 144 connected to the gas exhaust passage 138. Since each of the gassupply nozzles has a diameter of about 0.1 mm, a water componentremaining inside the gas supply ring 140 cannot be effectively removedby evacuating the gas by the high-vacuum pump 106 connected to theprocess chamber 102 thorough the gas supply nozzles. Accordingly, thegas supply ring 140 according to the present embodiment effectivelyremove the remainder such as a water component within the gas passage142 and the gas supply nozzles 143 through the outlet port 144 having anopening diameter much greater than that of the gas supply nozzles 143.

Similar to the gas supply nozzles 143, the gas supply nozzles 173 areprovided to the gas supply ring 170, which has the same structure as thegas supply ring 140. Accordingly, the gas supply ring 170 comprises amain part 176; an inlet port 171, an annular gas passage 172, aplurality of gas supply nozzles 173, an outlet port 174 and a nozzlepart 175. Similar to the gas supply ring 140, gas inside the gas supplyring 170 can be evacuated trough the outlet port 174 connected to thegas exhaust passage 168. Since each of the gas supply nozzles has adiameter of about 0.1 mm, a water component remaining inside the gassupply ring 170 cannot be effectively removed by evacuating the gas bythe high-vacuum pump 106 connected to the process chamber 102 thoroughthe gas supply nozzles. Accordingly, the gas supply ring 170 accordingto the present embodiment effectively remove the remainder such as awater component within the gas passage 172 and the gas supply nozzles173 through the outlet port 174 having an opening diameter much greaterthan that of the gas supply nozzles 173.

In the present embodiment, a vacuum pump 152 is connected to the gasexhaust passage 138, which is connected to the outlet port 144 of thegas supply ring 140, via a pressure adjust valve 151. Similarly, avacuum pump 154 is connected to the gas exhaust passage 168, which isconnected to the outlet port 164 of the gas supply ring 170, via apressure adjust valve 153. Each of the vacuum pumps 152 and 154 can aturbo-molecular pump, a sputter ion pump, a getter pump, a sorption pumpor a cryopump.

The pressure adjust pumps 151 and 153 are closed when the respectivevalves 132 and 162 are open, and are opened when the respective valves132 and 162 are closed. As a result, when a plasma process is performedby opening the valves 132 and 162, the vacuum pumps 152 and 154 aredisconnected from the respective gas supply system by the pressurecontrol valve 151 and 153 being closed so.,that the reactant gas and thedischarge gas are introduced into the process chamber 102. The vacuumpumps 152 and 154 are connected to the gas supply system be the pressureadjust valves 151 and 153 being open after completion of the plasmaprocess. That is, the vacuum pumps 152 and 154 can evacuate gas from therespective gas supply rings 140 and 170 during a period other than aperiod when the plasma process performed. Specifically, the vacuum pumps152 and 154 can be operated during a period for carrying the object Winto the process chamber or taking out of the process chamber 102 or aperiod for moving the susceptor 104. Accordingly, the vacuum pumps 152and 154 can evacuate the remaining gas from the gas supply rings 140 and170 to an extent that an influence of the remaining gas is negligible.Thereby, the gas supply nozzles 143 and 173 are prevented from beingclosed by impurities such as a water component remaining in the gassupply rings, thereby preventing an uneven introduction of the gas fromthe gas supply rings 140 and 170. Additionally, the object W to beprocessed is prevented from being contaminated by impurities dischargedfrom the gas supply rings 140 and 170. Thus, the vacuum pumps 152 and154 enables a high-quality plasma process being applied to the object Wto be processed.

In the present embodiment, a microwave is generated by a microwavegenerator 110. The microwave generator 110 comprises a magnetron, whichcan generate, for example, a 2.45-GHz microwave (for example, 5 kW). Themicrowave generated by the microwave generator 110 is converted into aTM mode, a TE mode or a TEM mode by a mode converter 112. It should benoted that, in FIG. 1, an isolator for absorbing a microwave returningto the microwave generator 110 and a stub tuner for load matching arenot shown for the sake of simplification of the figure.

The antenna member 120 comprises a temperature control plate 122, anantenna-accommodating member 123 and a dielectric plate 230. Thetemperature control plate 122 is connected to a temperature control unit121. The antenna-accommodating member 123 accommodates a slow-wavemember 124 and a slot electrode 200 that contacts the slow-wave member124. The dielectric plate 230 is positioned under the slot electrode200. The antenna-accommodating member 123 is made of a material havinghigh heat conductivity such as stainless steel. A temperature of theantenna accommodating member 123 can be controlled nearly equal to thetemperature of the temperature control plate 122.

The slow-wave member 124 is made of a material having a predeterminedpermittivity to reduce the wavelength of the microwave transmittedtherethrough. In order to make the plasma density in the process chamber102 uniform, many slits must be formed in the slot electrode 200. Thus,the slow-wave member 124 has a function to enable the formation of manyslits in the slot electrode 200. Ceramics such as SiN or AlN can be usedfor the slow-wave member 124. For example, the specific permittivityε_(t) of AlN is about 9 and, thus, the wavelength reducing rate n is0.33 (n=1/(ε_(t))^(1/2)=0.33). Accordingly, the transmission rate of themicrowave after passing through the slow-wave member 124 becomes 0.33times the original transmission rate, and, thus, the wavelength alsobecomes 0.33 times the original wavelength. Accordingly, a distancebetween adjacent slits 210 of the slot electrode 200 can be reduced,resulting in a larger number of slits 210 being provided in the slotelectrode 200. The slot electrode 200 is formed of a copper plate havinga circular shape whose diameter is, for example, about 50 cm andthickness is less than 1 mm. The slot electrode 200 is fixed to theslow-wave member 124 by screws.

The slot electrode 200 may be referred to as a radial inline slotantenna (RLSA) or an ultra high efficiency flat antenna. The presentinvention is not limited to such an antenna and other type antenna suchas a single layer waveguide flat antenna or a dielectric substrateparallel slot array may be used.

FIGS. 7, 8, 9 and 10 are plan views of examples of the slot antenna 200shown in FIG. 1. Hereinafter, the reference numerals such as 200generally represent all the reference numerals having a suffix such as200 a, 200 b, 200 c and 200 d. Any one of the slot electrodes 200 a, 200b, 200 c and 200 d can be used in the plasma processing apparatus 100shown in FIG. 1.

The slot electrode 200 has a plurality of T-slits 210 consisting of apairs of slits 212 and 214 arranged in a T-shape with a predetermineddistance therebetween. The T-slits 210 are arranged in a plurality ofareas or sections defined by virtually dividing the surface of the slotelectrode 200 on a one-to-one basis. In the slot electrode 200 a shownin FIG. 7, each of the virtually divided areas has a hexagonal shape. Inthe slot electrodes 200 b, 200 c and 200 d shown in FIGS. 8, 9 and 10,each of the virtually divided areas has a square shape. It should benoted that each of the T-slits 210 d of the slot electrode 200 d shownin FIG. 10 is a variation of the T-slit 210, and the actual shape formedby the slits 211 d and 214 d is similar to V-shape.

The T-slits 210 are arranged on the surface of the slot electrode 200 sothat the density of the T-slits 210 is substantially uniform over theentire surface of the electrode 200. This is to prevent an isolation ofthe 10 material forming the dielectric plate 230 so as to prevent theisolated material as impurities from being mixed to a reactant gas.Since the slot electrode 200 can provide a substantially uniformdistribution of ion energy to the dielectric plate 230, the dielectricplate 230 is prevented from being isolated which results in ahigh-quality plasma process being achieved.

As mentioned above, each T-slit 210 comprises a pair of slits 212 and214 forming a T-shape with a predetermined distance therebetween. Morespecifically, each of the slits 212 and 214 has a length L1 which is inthe range of about one half of the wavelength λ₀ of the microwave to 2.5times a free space wavelength. The width of each of the slits 212 and214 is about 1 mm. A distance L2 between two adjacent pairs of slitsalong a radial direction is approximately equal to the wavelength λ₀.That is, the length L1 of each of the slits 212 and 214 is set tosatisfy the following relationship.(λ₀/2×1/√{square root over ( )}ε_(t))≦L1≦(λ₀×2.5)

By setting each of the slits 212 and 214 to the above-mentionedstructure, a uniformly distributed microwave can be achieved in theprocess chamber 102.

Each of the slits 212 and 214 is slanted with respect to a radial lineconnecting the center of the slot electrode 200 and an intersectingpoint between longitudinal axes of the slits 214 and 214. The size ofthe T-slits 210 becomes larger as a distance from the center of the slotelectrode 200 increases. For example, if the distance from the center istwice, the size of each of the slits 212 and 214 is increased to about1.2 to 2 times.

It should be noted that the shape of the slits 210 and their arrangementare not limited to that shown in FIGS. 7, 8, 9 and 10 as long as thedensity of the slits can be uniform over the surface of the slotelectrode 200. That is, the configuration of the pair of slits 212 and214 is not limited to the above-mentioned shape, and, for example,L-shaped slits may be used for the slot electrode 200. Additionally, theshape of each of the virtually divided areas is not limited to thehexagonal shape or the square shape, and an arbitrary shape such as atriangular shape may be adopted. Accordingly, the virtually dividedareas may be different in their shape and size. Further, the slits 210may be arranged along a plurality of concentric circles or a spiralalthough the density of the slits may not be uniform.

A radiation element having a width of a few millimeters may be providedon the periphery of the slot electrode 200 so as to prevent reflectionof the microwave transmitted toward the periphery of the slot electrode200. The radiation element provided for increasing an antenna efficiencyof the slot electrode 200.

The temperature control plate 122 serves to control the temperaturechange of the antenna-accommodating member 123 and component parts nearthe antenna-accommodating member 123 to fall within a predeterminedrange. A temperature sensor and a heater unit (both not shown in thefigure) are connected to the temperature control plate 122. Thetemperature control unit 121 controls a temperature of the temperaturecontrol plate 122 to be a predetermined temperature by introducing acooling water or a coolant such as alcohol, gulden or flon into thetemperature control plate 122. The temperature control plate 122 is madeof a material such as stainless steel, which has high heat conductivityand can be machined to form a fluid passage for the cooling watertherein.

The temperature control plate 122 contacts the antenna-accommodatingmember 123, and each of the antenna accommodating member 123 and theslow-wave member 124 has high heat conductivity. Accordingly, thetemperature of each of the slow-wave member 124 and the slot electrode200 can be controlled by merely controlling the temperature of thetemperature control plate 122. The temperature of each of the slow-wavemember 124 and the slot electrode 200 is increased due to energyabsorption when the microwave of the microwave generator 110 is suppliedthereto for a long period of time. As a result, each of the slow-wavemember 124 and the slot electrode 200 may deform due to thermalexpansion.

For example, if the slot electrode 200 thermally deforms, the length ofeach slit is changed, which results in a decrease in the plasma densityor localization of the plasma in the process chamber 102. The decreasein the plasma density may slow down a plasma processing speed such as anetching rate or a film deposition rate. As a result, if the plasmaprocessing is controlled based on a processing time, there may be a casein which a desired result of the plasma processing (such as plasmaetching depth or plasma deposition thickness) cannot be obtained whenthe plasma processing is applied for a predetermined time period (forexample, two minutes), that is, for example, if the object W isprocessed for a predetermined time (for example, two minutes) andthereafter removed from the process chamber 102. Additionally, if theplasma density in the process chamber 102 is localized, the magnitude ofplasma processing applied to the semiconductor wafer may vary. Asmentioned above, if a deformation occurs in the slot electrode 200, thequality of plasma processing may deteriorate.

Further, if the temperature control plate 122 is not provided, the slotelectrode 200 may warp since the materials of the slow-wave member 124and the slot electrode 200 are different from each other and bothmembers are fixed to each other by screws. In such a case, the qualityof plasma processing may deteriorate for a reason similar to theabove-mentioned reason.

A dielectric plate 230 is provided between the slot electrode 200 andthe process chamber 102 so as to close the top opening of the processchamber 102. The slot electrode 200 is tightly joined to the surface ofthe dielectric plate 230 by brazing. Alternatively, the slot electrode200 can be formed by a copper plate applied to the surface of thedielectric plate 230.

It should be noted that the function of the temperature control plate122 may be provided to the dielectric plate 230. That is, thetemperature of the dielectric plate 230 can be controlled by integrallyforming a temperature control plate with the dielectric plate 230, whichtemperature control plate has a coolant passage near the side of thedielectric plate 230. By controlling the temperature of the dielectricplate 230, the temperature of the slow-wave member 124 and the slotelectrode 200 can be controlled. The dielectric plate 230 is mounted tothe process chamber 102 with an O-ring provided therebetween.Accordingly, the temperature of the dielectric plate 230 can becontrolled by controlling a temperature of the O-ring, and, therebycontrolling the temperature of the slow-wave member 124 and the slotelectrode 200.

The dielectric plate 230 is made of a dielectric material such asaluminum nitride (AlN). The dielectric plate 230 prevents the slotelectrode 200 from being deformed due to a negative pressure generatedin the process chamber 102. Additionally, the dielectric plate 230prevents the slot electrode 200 from being exposed to the atmosphereinside the process chamber 102 so that the environment inside theprocess chamber 102 is prevented from being contaminated by copper. Ifnecessary, the dielectric plate 230 may be formed of a dielectricmaterial having a low heat conductivity so as to prevent the slotelectrode 200 from being influenced by heat from the process chamber102.

In the present embodiment, the thickness of the dielectric plate 230 isgreater than 0.5 times the wavelength of the microwave in the dielectricplate 230 and smaller than 0.75 times the wavelength of the microwave inthe dielectric plate 230. Preferably, the thickness is in the range of0.6 to 0.7 times the wavelength of the microwave in the dielectric plate230. The 2.45 GHz microwave has a wavelength of about 122.5 mm in avacuum. If the dielectric plate 230 is made of aluminum nitride (AlN),the wavelength reducing rate n is equal to 0.33 since the specificpermittivity ε_(t) is about 9 as mentioned above. Accordingly, thewavelength of the microwave in the dielectric plate 230 is about 40.8mm. Thus, if the dielectric plate 230 is formed of AN, the thickness ofthe dielectric plate 230 is preferably greater than about 20.4 mm andsmaller than about 30.6 mm, and, more preferably within a range fromabout 24.5 mm to about 28.6 mm. In general, the thickness H of thedielectric plate 230 preferably satisfies a relationship 0.5λ<H<0.75λ,and, more preferably, 0.6λ≦H≦0.7λ. The wavelength λ of the microwave inthe dielectric material 230 satisfies λ=λ₀n, where λ₀ is a wavelength ofthe microwave in the vacuum and n is a wavelength reducing rate(n=1/ε_(t) ^(1/2)).

When the thickness of the dielectric plate 230 is 0.5 times thewavelength of the microwave in the dielectric plate 230, a standing waveis generated as a resultant wave of a synthesis of a progressing wavetraveling along the front surface of the dielectric plate 230 and aregressive wave reflected by the back surface of the dielectric plate230. Thereby, the reflection is maximized and a power of the microwavetransmitted to the process chamber 102 is minimized as shown in FIG. 11,which is a graph showing a relationship between a transmission power ofthe microwave and the thickness of the dielectric plate. In such a case,generation of plasma is insufficient, and, thereby a desired processspeed cannot be achieved.

On the other hand, when thickness of the dielectric plate 230 is 0.75times the wavelength of the microwave in the dielectric plate 230, thetransmission power of the microwave is maximized but ion energy in theplasma is also maximized. The inventors found that the dielectricmaterial of the dielectric plate 230 isolates by a plasma ion energyapplied by transmission of a microwave isolates the material of thedielectric plate 230 as shown in FIG. 12. FIG. 12 is a graph showing arelationship between the thickness of the dielectric plate 230 and anamount of isolation (sputtering rate) of the dielectric plate 230. Ifthe material of the dielectric plate 230 isolates, the material entersthe object W to be processed as impurities, thereby deteriorating ahigh-quality plasma process.

Accordingly in the present embodiment, the thickness H of the dielectricplate 230 is set to a value ranging from 0.3λ to 0.4λ (0.3λ≦H≦0.4λ) or avalue ranging from 0.6λ to 0.7λ (0.6λ≦H≦0.7λ) as shown in FIG. 13. Thethickness H of the dielectric plates 230 may be set to a value rangingfrom 0.8λ to 0.9λ (0.8λ≦H≦0.9λ) or a value ranging from 1.1λ to 1.2λ(1.1λ≦H≦1.2λ) although the thickness H of the dielectric plates 230 isincreased. In more general form, the thickness H of the dielectric plate230 is set to a value ranging from (0.1+0.5N)λ to (0.2+0.5N)λ or a valueranging from (0.6+0.5N)λ to (0.7+0.5N)λ, where N is an integer. In otherwords, the thickness H of the dielectric plate 230 satisfies arelationship (0.1+0.5N)λ≦H≦(0.2+0.5N)λ or (0.6+0.5N)λ≦H≦(0.7+0.5N)λ.Considering a mechanical strength of the dielectric plate 230, thethickness H of the dielectric plate 230 is preferably set to a valueranging from 0.6λ to 0.7λ. However, for example, if the dielectric plate230 is made of quartz having a specific permittivity of 3.8, a valueranging from 0.3λ to 0.4λ or a value ranging from 0.1λ to 0.2λ may beused. Additionally, the above-mentioned relationship in general form isapplicable to a wave used for generating plasma other than a microwave.

Since the gas supply systems 130 and 160 are arranged to supply areactant gas and a discharge gas from the nozzles 143 and 173,respectively, the gasses may traverse the surface of the object W to beprocessed. Accordingly, a uniform the plasma density cannot be achievedeven if the nozzles 143 and 173 are arranged in symmetric positions withrespect to the center of the susceptor 104. In order to solve such aproblem, it is considered to provide a showerhead structure made ofglass above the susceptor 104. A description will be given, withreference to FIG. 14, of such a showerhead structure. FIG. 14 is anillustrative cross-sectional view of a showerhead having a gas supplyarrangement.

The showerhead shown in FIG. 14 comprises a dielectric plate 240 and ashower plate 250. It should be noted that the dielectric plate 240 andthe shower plate 250 may be integrally formed with each other by adielectric material. The dielectric plate 240 is formed of an aluminumnitride (AlN) plate having a thickness of 30 mm. The shower plate 250 isattached to a bottom surface of the dielectric plate 240. The dielectricplate 240 has an inlet port 241, a gas passage 242 and an outlet port244.

The gas supply passage 136 of the gas supply system 130 is connected tothe inlet port of the dielectric plate 240. The gas exhaust passage 138is connected to the outlet port 144 of the dielectric plate 240.Although the dielectric plate 240 shown in FIG. 14 is applied to the gassupply system 130, a mixture of the gasses supplied by the gas supplysystems 130 and 160 may be supplied to the inlet port 141 of thedielectric plate 240. A plurality of the inlet ports 141 may be providedto the dielectric plate 241 so that a gas supplied through the inletports 241 is uniformly introduced into the process chamber through theshowerhead. Additionally, a part of the inlet ports 241 may be connectedto the gas supply passage 136, and the rest of the inlet ports 241 maybe connected to the gas supply passage 166.

Alternatively, the gas supply system 160 may be provided to the sidewallof the process chamber as shown in FIG. 1. This is because the dischargegas such as argon is not easily decomposed as compared to silane ormethane, and, thus, the uniformity of the plasma density is not sodeteriorated if the discharge gas is introduced into the process chamber102 from the side.

A shown in FIG. 14, the outlet port 144 of the dielectric plate 240 isconnected to the gas exhaust passage 138, which is connected to thevacuum pump 152 via the pressure adjust valve 151. The function of thevacuum pump 151 is the same as that described above, and a descriptionthereof will be omitted.

A description will now be give, with reference to FIG. 15, of astructure of the shower plate 250 shown in FIG. 14. FIG. 15 is anenlarged cross-sectional view of a part of the shower plate 250 whichpart includes one of nozzles 253 provided to the shower plate 250. Asshown in FIG. 15, the dielectric plate 240 has recessed portions 246 atpositions corresponding to the nozzles 253 of the shower plate 250.

The shower plate 250 is made of an aluminum nitride (AlN) plate having athickness of about 6 mm. The shower plate 250 has a plurality of nozzles253 positioned in a predetermined uniform arrangement. As shown in FIG.15, each of the nozzles 253 is provided with an eject member 260. Theeject member 260 is constituted by a screw (262 and 264) and a nut 266.

The screw head 262 has a height of about 2 mm. A pair of eject passages269 are formed in the screw head 262. Each of the eject passages 269extends from the center of the screw head 262 in a direction inclined 45degrees with respect to the bottom surface 256 of the shower plate 250.An end of each of the eject passages 269 is connected to a nozzlepassage 268 formed in the screw part 254. Each of the eject passages 269has a diameter of about 0.1 mm. The eject passages 269 are inclined soas to achieve a uniform introduction of the reaction gas. Accordingly,the number of the eject passages 269 and their angle with respect to theshower plate 250 may be changed so as to achieve uniform distribution ofthe reaction gas. It should be noted that, according to experimentsconducted by the inventors, uniform distribution of the reaction gas wasnot achieved by a single ejecting passage extending in a directionperpendicular to the surface 256 of the shower plate 250. It was foundthat the eject passage 269 is preferably inclined so as to achieveuniform distribution of the reaction gas.

The nozzle passage 268 formed in the screw part 264 has a diameter ofabout 1 mm, and extends in a longitudinal direction of the screw part264. An end of the nozzle passage 268 is open to a gap space 242 formedbetween the dielectric plate 240 and the shower plate 250. The screwpart 264 is inserted into a through hole formed in the shower plate 250,and the screw is fastened to the shower plate 250 by the nut 266 beingengaged with the end of the screw part 264. The nut 266 is accommodatedin the recessed portion 246 formed on the surface of the dielectricplate 240 facing the shower plate 250.

The gap space 242 is provided for preventing generation of plasma. Thethickness of the gap space 242 required for preventing generation ofplasma varies according to a pressure of the reactant gas. That is, forexample, the thickness of the gap space 242 is set to about 0.5 mm whenthe pressure is 10 Torr. In this case, the process space under theshower plate 250 in the process chamber 102 is set to a pressure ofabout 50 mtorr. The reactant gas is introduced into the process chamber.102 at a predetermined speed by controlling the pressure differencebetween the reactant gas and the atmosphere in the process chamber 102.

According to the shower plate 250 provided in the present embodiment,the reactant gas can be uniformly introduced and distributed in theprocess space in the process chamber 102 without generation of plasmabefore reaching the process space. An amount of flow of the reaction gascan be controlled according to the pressure difference between the gapspace 242 and the process space in the process chamber 102, the numberof eject passages 269, the inclination angle of the eject passages 269and the size of each of the eject passages 269.

The eject member 260 may be integrally formed with a part or a whole ofthe shower plate 250, and can be any shape. For example, the ejectmember 260 may be replaced by eject members shown in FIGS. 16, 17 and18. FIG. 16 is an enlarged cross-sectional view of the eject member 350a provided with a nozzle passage 352 a having a single nozzle opening354 a. FIG. 17 is an enlarged cross-sectional view of the eject member350 b provided with a nozzle passage 352 b having two nozzle openings354 b. FIG. 18 is an enlarged cross-sectional view of the eject member350 c provided with a nozzle passage 352 c having three nozzle openings354 c.

A description will now be given, with reference to FIG. 19, of a clustertool that can be connected to the plasma processing apparatus 100 shownin FIG. 1. FIG. 19 is an illustrative plan view of the cluster tool 300that is connectable to the microwave plasma processing apparatus 100shown in FIG. 1. As mentioned above., the temperature of the object Wcan be controlled by the susceptor 104. However, in a CVD process, ittakes a considerable time to raise the temperature of the object W froma room temperature to about 250° C. to 350° C. by the susceptor 104. Inorder to eliminate such a problem, the cluster tool 300 heats the objectW prior to providing the object W to the process chamber 102 of themicrowave plasma processing apparatus 100. Similarly, it takes aconsiderable time to decrease the temperature of the object W from 250°C. to 350° C. to a room temperature by the susceptor 104 after theplasma processing is completed. In order to eliminate such a problem,the cluster tool 300 cools the object W prior to starting anotherprocess after the object W is taken out of the process chamber 102 ofthe microwave plasma processing apparatus 100.

As illustratively shown in FIG. 19, the cluster tool 300 comprises: aconveyor section 320 including a conveyor arm which holds and conveysthe object W to be processed; a preheating section 340 for heating theobject W; a cooling section 360 for cooling the object W; and load-lock(L/L) chambers 380. In FIG. 19, two process chambers 102A and 102B areshown. Each of the process chambers 102A and 102B can be the processchamber 102 of the microwave plasma processing apparatus 100 shown inFIG. 1. The number of process chambers provided in the cluster tool 300is not limited to two.

The conveyor section 320 is provided with the conveyor arm which holdsthe object W and a rotating mechanism for rotating the conveyor arm. Thepreheating section 340 is provided with a heater so as to heat theobject W to a temperature close to a process temperature before theobject W is placed in the process chamber 102A or 102B. The coolingsection 340 is provided with a cooling chamber, which is cooled by acoolant so as to cool the object W taken out of the process chamber 102Aor 102B to a room temperature before the object W is conveyed to asubsequent apparatus such as an ion implantation apparatus or an etchingapparatus. Preferably, the cluster tool 300 comprises a rotational anglesensor, a temperature sensor, at least one control unit and a memory forstoring control programs so as to control the rotation of the conveyorarm of the conveyor section 320 and control a temperature of each of thepreheating section 340 and cooling section 360. Such a sensor, a controlunit and a control program are known in the art, and descriptionsthereof will be omitted. Additionally, the conveyor arm of the conveyorsection 320 places the object W in the process chamber 102A or 102Bthrough the gate valve 101.

A description will now be given of an operation of the microwave plasmaprocessing apparatus 100 shown in FIG. 1. First, the conveyor arm of theconveyor section 320 shown in FIG. 19 holds the object W to be processedso as to place the object W in the process chamber 102 (in FIG. 19, oneof the process chambers 102A and 102B corresponds to the process chamber102). It is assumed that the object W is subjected to a CVD process inthe process chamber 102. In such as case, the control unit (not shown inthe figure) of the cluster tool 300 sends an instruction to the conveyorsection 320 to convey the object W to the preheating section 340 so asto heat the object W to a temperature of about 300° C. before placingthe object W in the process chamber 102.

For example, the cluster tool 300 forms a silicon oxidation film on asilicon substrate in the process chamber 102A by applying a plasmaprocess. Thereafter the cluster tool 300 transfers the silicon substrateto the process chamber B so as to form a silicon nitride film by plasmaprocessing the silicon oxidation film by introducing nitrogen into theprocess chamber 102B. A reactant gas introduced into the process chamber102A so as to form the silicon oxidation film is typically SiH₄—N₂O.However, instead of SiH₄, TEOS (tetraethylorthosilicate), TMCTS(tetramethylcyclotetrasiloxane) or DADBS(diacetoxyditertiarybutoxysilane) may be used. The reactant gasintroduced into the process chamber 102B is typically SiH₄—NH₃. However,instead of SiH₄, SiF₆, NF₃ or SiF₄ may be used.

Upon receiving the instruction, the conveyor section 320 moves theobject W to the preheating section 340 so as to heat the object W. Whenthe temperature sensor (not shown in the figure) of the cluster tool 300detects that the object W to be processed is heated to a temperature ofabout 300° C., the control unit of the cluster tool 300 sends aninstruction to the conveyor section 320 to move the object W to beprocessed from the preheating section 340 to the process chamber 102through the gate valve 101. Accordingly, the conveyor arm of theconveyor section 320 conveys the heated object W to the process chamber102 through the gate valve 101. When the heated object W reaches aposition above the susceptor 104 in the process chamber 102, the lifterpin vertically moving system moves the lifter pins (not shown in thefigure) so as to support the object W by the three lifter pins (notshown in the figure) protruding from the upper surface of the susceptor104. After the object W is transferred from the conveyor arm to thelifter pins, the conveyor arm returns through the gate vale 101.Thereafter, the conveyor arm may be moved to a home position (not shownin the figure).

After the object W is transferred to the lifter pins, the verticalmoving unit 146 moves the vertical moving member 142 downward so as toreturn the lifter pins inside the susceptor 104 and place the object Won the susceptor 104. At this time, a susceptor moving member can bemoved while maintaining the hermetic seal of the process chamber 102 bya bellows (not shown in the figure). The susceptor 104 heats the objectW placed thereon to a temperature of 300° C. At this time, since theobject W is preheated, it takes a short time to completely the processpreparation. More specifically, the heater control unit 191 controls theheater unit 198 so as to raise the temperature of the susceptor 104 to300° C.

Thereafter, the high-vacuum pump 106 maintains the pressure in theprocess chamber 102 at 50 mTorr by being controlled by the pressureadjust valve. Additionally, the valves 151 and 153 are opened, and thevacuum pumps 152 and 154 evacuate gas form the gas supply rings 140 and170. As a result, a water component remaining in the gas supply rings140 and 170 is sufficiently removed therefrom.

Additionally, the susceptor vertically moving system moves the susceptor104 and the object W to a predetermined process position from a homeposition. The bellows (not shown in the figure) maintains the negativepressure environment in the process chamber 102 during the verticallymoving operation, and prevents an atmosphere from exiting outside theprocess chamber 102. Thereafter, the valves 151 and 153 are closed.

Thereafter, the valves 132 and 162 are opened so as to introduce amixture of NH3, helium, nitrogen and hydrogen into the process chamber102 from the gas supply rings 140 and 170 via the mass flow controllers134 and 164. Since the valves 151 and 153 are closed, the vacuum pump152 and 154 do not evacuate the gases in the gas supply systems 130 and160 from being introduced into the process chamber 102.

When the shower plate 250 shown in FIG. 14 is used, the process chamber102 is maintained, for example, at 50 mTorr, and a mixture of helium,nitrogen, hydrogen and NH₃, for example, is supplied to the dielectricplate 240. Thereafter, the mixture gas is introduced into the processchamber by being passed through the gap space 242, the recessed portions246 and the nozzle passages 268 and 269 of the eject members 260. Themixture gas is not converted into plasma, and is introduced into theprocess chamber 102 with a high controllability of flow and a uniformdensity.

The temperature of the process space of the process chamber 102 isadjusted to be 300° C. A microwave is generated by the microwavegenerator 110, and is supplied to the wavelength-reducing member 124 ofthe antenna member 120 in a TEM mode via a square waveguide or a coaxialwaveguide. The microwave passing through the wavelength-reducing member124 is reduced in its wavelength, and enters the slot electrode 200. Themicrowave is then introduced into the process chamber 102 via the slits210 and the dielectric material plate 230. Since a temperature of thewavelength reducing member 124 and the slot electrode 200 is controlled,there is no deformation due to thermal expansion. Accordingly, anoptimum length of the slits 210 can be maintained. Thus, the microwavecan be introduced into the process chamber 102 at a desired densitywithout local concentration.

Thereafter, the reactant gas in the process chamber 102 is convertedinto plasma by the microwave, and a plasma CVD process is performed onthe object W placed on the susceptor 104. If the baffle plate 194 isused, the baffle plate maintains the potential in the process space soas to prevent the microwave from exiting the process space. Thus, adesired process speed can be maintained.

If a temperature of the susceptor 104 is raised higher than apredetermined upper limit temperature due to continuous use, thesusceptor 104 is cooled by the temperature control unit 191. On theother hand, if the temperature of the susceptor 104 is below apredetermined lower limit temperature at an initial stage of theoperation of the apparatus or when the susceptor 104 is over cooled, thetemperature control unit 191 heats the susceptor 104.

The plasma CVD process is continued for a predetermined period of time(for example, about 2 minutes). Thereafter, the object W is taken but ofthe process chamber 102 through the gate valve 101 by the conveyorsection 320 of the cluster tool 300 in a reversed way of theabove-mentioned procedure. When the susceptor 104 is taken out, thevertically moving mechanism (not shown in the figure) returns thesusceptor 104 and the object W to the home position. The predeterminedprocess time of 2 minutes is determined by a CVD processing timegenerally required for forming the layered nitride film. That is, evenif the temperature control unit 190 sets the temperature to about 250°C. to 350° C., a long time deposition process may cause a problemsimilar to when the temperature is set higher than 350° C. Additionally,if the process time is too short, there may be a case in which asemiconductor element produced from the object W cannot effectivelyprevent a leak current.

Since the microwave is uniformly supplied to the process chamber 102with a predetermined density, a silicon oxidation film and a siliconnitride film having a desired thickness are formed on the object W to beprocessed. Additionally, since the temperature of the process chamber102 is maintained in the predetermined range so that a water component(impurities) does not enter the object W, the deposited film can bemaintained at a desired quality. The object W taken out of the processchamber 102 is transferred to the cooling section 360 and the object Wis cooled to a room temperature in a short time. Then, if necessary, theobject W is conveyed by the conveyor section 320 to a next stageapparatus such as an ion implantation apparatus.

A description will now be given, with reference to FIG. 20, of a secondembodiment of the present invention. FIG. 20 is an illustration of astructure of a microwave plasma processing apparatus 400 according tothe second embodiment of the present invention. In FIG. 20, parts thatare the same as the parts shown in FIG. 1 are given the same referencenumerals, and descriptions thereof will be omitted.

Similar to the first embodiment, the second embodiment of the presentinvention is specifically related to an evacuating arrangement toevacuate gas from a gas-introducing part provided in a process chamberof the microwave plasma processing apparatus 400. In the firstembodiment, the evacuating arrangement is comprised of the vacuum pump151 or 153, which evacuates gas remaining in the gas supply ring 140 or170. On the other hand, in the second embodiment, the evacuatingarrangement is comprised of a bypass passage, which directly connectsthe gas supply ring 140 or 170 to the vacuum pump 106 by bypassing theprocess chamber 102.

More specifically, in the plasma processing apparatus 400 according tothe second embodiment, the outlet port of the gas supply ring 140 isconnected to an end of a bypass passage 182, and the other end of thebypass passage 182 is connected to the vacuum pump 106, which isoriginally provided to the plasma processing apparatus 400 so as toevacuate gas from the process chamber 102. Additionally, a valve 181 isprovided to the bypass passage 182 so as to open or close the bypasspassage 182. Similarly, the outlet port of the gas supply ring 170 isconnected to an end of a bypass passage 184, and the other end of thebypass passage 184 is connected to the vacuum pump 106. Additionally, avalve 183 is provided to the bypass passage 184 so as to open or closethe bypass passage 184. FIG. 21 is an illustration of the evacuatingarrangement of the above-mentioned gas-evacuating arrangement.

In the present embodiment, each of the bypass passages 182 and 184 has adiameter of 25 mm to 40 mm, which is greater than the diameter of thegas supply nozzles 143 and 172. Thus, the vacuum pump 106 can evacuategas remaining in the gas supply rings 140 and 170 more efficiently andmore rapidly than when the gas is evacuated through the gas supplynozzles 143 and 173. It should be noted that although the bypasspassages 182 and 184 are connected to the high-vacuum pump 106, thebypass passages 182 and 184 may be connected to a roughing pump or othervacuum pumps originally provided to the plasma processing apparatus 400.

In the present embodiment, the gas supply system 130 or 160 may bearranged to use the dielectric plate 240 and the shower plate 250 asshown in FIG. 14. In such a case, the outlet port 244 of the dielectricpate is connected to the bypass passage 182 or 184 so that the gaspassage 242 is connected to the vacuum pump 6 by bypassing the processchamber 102.

It should be noted that the microwave plasma processing apparatuses 100and 400 can utilize an electron. cyclotron resonance, and therefore, anelectromagnetic coil may be provided so as to generate a magnetic fieldin the process chamber 102. Additionally, although the microwave plasmaprocessing apparatus 100 according to the present embodiment performsthe plasma CVD process as plasma processing, the plasma processing isnot limited to the plasma CVD process. That is, for example, a plasmaetching process or a plasma cleaning process may be performed by themicrowave plasma processing apparatus 100. Additionally, the presentinvention is not limited to the RLSA type plasma processing apparatus,and may be applied to a parallel plate plasma processing apparatusutilizing a grow discharge. Further, the object W to be processed by themicrowave plasma processing apparatus 100 is not limited to the waferfor producing a semiconductor device, and the microwave plasmaprocessing apparatus 100 may be used to process an LCD substrate or aglass substrate.

The present invention is not limited to the specifically disclosedembodiments, and variations and modifications may be made withoutdeparting from the scope of the present invention.

The present application is based on Japanese priority application No.2000-085351 filed on Mar. 24, 2000, the entire contents of which arehereby incorporated by reference.

1. A plasma processing method for forming a silicon nitride film on asilicon oxide film, the plasma processing method comprising: preparing asubstrate on which said silicon oxide film is formed; generating plasmaby supplying a nitrogen gas onto said silicon oxide film; andnitride-processing said silicon oxide film by said plasma so as tomodify an upper portion of said silicon oxide film into the siliconnitride film.
 2. The plasma processing method as claimed in claim 1,wherein a nitrogen concentration at an interface between said siliconoxide film and said silicon nitride film is lower than that of saidsilicon oxide film under said silicon nitride film.
 3. A plasmaprocessing method for forming a silicon nitride film, comprising:preparing a substrate on which a silicon oxide film is formed;generating plasma by supplying a nitrogen gas onto said silicon oxidefilm; and nitride-processing an upper portion of said silicon oxide filmby said plasma so as to modify the upper portion of said silicon oxidefilm into the silicon nitride film, wherein said plasma is generated byirradiating a microwave to the nitrogen gas via a planar antenna havinga plurality of slits.
 4. The plasma processing method as claim in claim3, wherein a nitrogen concentration at an interface between said siliconoxide film and said substrate is lower than that of said silicon oxidefilm under said silicon nitride film.
 5. A plasma processing method forforming a silicon nitride film, comprising: preparing a siliconsubstrate; generating plasma by supplying a nitrogen gas onto saidsilicon substrate; and nitride-processing an upper portion of saidsilicon substrate directly by said plasma so as to form the siliconnitride film, wherein, in the nitride-processing, the processing by saidplasma is performed after setting a temperature of said siliconsubstrate at 450° C. or higher.
 6. The plasma processing apparatus asclaimed in claim 5, wherein said plasma is generated by irradiating amicrowave to the nitrogen gas via a planar antenna having a plurality ofslits.
 7. A plasma processing method for forming a silicon nitride film,comprising: preparing a substrate; generating plasma by supplying anitrogen gas onto said silicon substrate film; and nitride-processing anupper portion of said silicon substrate directly by said plasma so as toform the silicon nitride film, wherein said plasma is generated byirradiating a microwave to the nitrogen gas via a planar antenna havinga plurality of slits, and the processing by said plasma is performedafter setting a temperature of said silicon substrate at 450° C. orhigher.